title: SERCA2 activity is involved in the CNP-mediated functional responses in failing rat myocardium.
abstract: OBJECTIVE
  Myocardial C-type natriuretic peptide (CNP) levels are increased in heart failure. CNP can induce negative inotropic (NIR) and positive lusitropic responses (LR) in normal hearts, but its effects in failing hearts are not known. We studied the mechanism of CNP-induced NIR and LR in failing hearts and determined whether sarcoplasmatic reticulum Ca(2+) ATPase2 (SERCA2) activity is essential for these responses.
  
  
  METHODS
  Contractility, cGMP levels, Ca(2+) transient amplitudes and protein phosphorylation were measured in left ventricular muscle strips or ventricular cardiomyocytes from failing hearts of Wistar rats 6 weeks after myocardial infarction.
  
  
  RESULTS
  CNP increased cGMP levels, evoked a NIR and LR in muscle strips, and caused phospholamban (PLB) Ser(16) and troponin I (TnI) Ser(23/24) phosphorylation in cardiomyocytes. Both the NIR and LR induced by CNP were reduced in the presence of a PKG blocker/cGMP analogue (Rp-8-Br-Pet-cGMPS) and the SERCA inhibitor thapsigargin. CNP increased the amplitude of the Ca(2+) transient and increased SERCA2 activity in cardiomyocytes. The CNP-elicited NIR and LR were not affected by the L-type Ca(2+) channel activator BAY-K8644, but were abolished in the presence of isoprenaline (induces maximal activation of cAMP pathway). This suggests that phosphorylation of PLB and TnI by CNP causes both a NIR and LR. The NIR to CNP in mouse heart was abolished 8 weeks after cardiomyocyte-specific inactivation of the SERCA2 gene.
  
  
  CONCLUSIONS
  We conclude that CNP-induced PLB and TnI phosphorylation by PKG in concert mediate both a predictable LR as well as the less expected NIR in failing hearts.
authors.affiliation: Department of Pharmacology, Faculty of Medicine, University of Oslo and Oslo University Hospital, Oslo, Norway; KG Jebsen Cardiac Research Centre and Center for Heart Failure Research, Faculty of Medicine, University of Oslo, Oslo, Norway.
authors.forename: L R
authors.initials: LR
authors.lastname: Moltzau
authors.forename: J M
authors.initials: JM
authors.lastname: Aronsen
authors.forename: S
authors.initials: S
authors.lastname: Meier
authors.forename: C H T
authors.initials: CH
authors.lastname: Nguyen
authors.forename: K
authors.initials: K
authors.lastname: Hougen
authors.forename: Ø
authors.initials: Ø
authors.lastname: Ørstavik
authors.forename: I
authors.initials: I
authors.lastname: Sjaastad
authors.forename: G
authors.initials: G
authors.lastname: Christensen
authors.forename: T
authors.initials: T
authors.lastname: Skomedal
authors.forename: J-B
authors.initials: JB
authors.lastname: Osnes
authors.forename: F O
authors.initials: FO
authors.lastname: Levy
authors.forename: E
authors.initials: E
authors.lastname: Qvigstad
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D006333:Heart Failure / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000503:physiopathology*; D009206:Myocardium / Q000473:pathology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D020098:Natriuretic Peptide, C-Type / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D019210:Troponin I / Q000378:metabolism; D000099211:Phospholamban
chemical_list: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002135:Calcium-Binding Proteins; D006152:Cyclic GMP; D017869:Cyclic GMP-Dependent Protein Kinases; D007545:Isoproterenol; D020098:Natriuretic Peptide, C-Type; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019284:Thapsigargin; D013873:Thionucleotides; D019210:Troponin I; D000099211:Phospholamban; C506948:Atp2a2 protein, rat; C098740:8-bromo-beta-phenyl-1,N(2)-ethenoguanosine 3',5'-cyclic monophosphorothioate; C506947:Atp2a2 protein, mouse
keywords: C-type natriuretic peptide; heart failure; lusitropic response; negative inotropic response; sarcoplasmatic reticulum Ca2+ ATPase; troponin I